My phone is always on WiFi unless I am in my car driving from place to place. I use under 2GB a month, closer to 1GB most months. I can't even comprehend how you would use 100GB of data on a mobile device in a month. My primary internet consumption is sitting at a computer all day long, or a laptop on the couch. The mobile data is just for traffic, slack, email, and news. All my podcasts are downloaded on WiFi, all my music is as well. There is just no reason for me to use any real amount of data while not on WiFi.

You live an urban lifestyle where you commute and travel by train and you don't stay in your suburban palace most of the time when you're not at work. Then you look at youtube videos during that time.

uhm, yeah, the sim card was in a mobile "pocket router" and shared to phone(s) + tablet + laptop, and I'm sometimes watching multiple streaming videos at the same time as a way of mixing music (Bach + heavy metal instrumental rocks :P) without bothering to turn video off or to low qual even if I'm not watching it

Unless you're consuming a lot of media, multiple GB is a lot. I have a super cheap plan with 500MB/month. It might sound impossible, but really all I have to do is turn off background mobile data for most apps, which had no business constantly sucking bytes anyway. Bonus, now my battery life is better.

If you have no WiFi access it's a somewhat different story, but WiFi is ubiquitous.

I know a few people in France who actually ditched their landline contract, they had full 4G coverage but were still at 8mbps with their landline. So now they're doing tethering for the complete house instead. The only thing they can't do is gaming because the ping is atrocious.

It's also cheaper, a 4G contract with a 100GB cap is about 15€ per month, whereas my FTTH connection at 900Mbps down / 400Mbps up cost me 40€ per month.

If you stream Pandora, Spotify, or a few podcasts in your daily commute, you'll eat up 3GB pretty easily.